Investigation of the Wettability and the Heat Transfer on Laser-Manufactured Complex Surfaces during Vapour Condensation at Saturated and Superheated Condition

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The main task in this project is to systematically and selectively modify the surface quality of sub-cooled substrates by means of laser manufacturing technology, such that a significant improvement in heat dissipation during steam condensation is achieved. It should be noted that, compared with non-modified surfaces, the increase in heat dissipation is achieved at equivalent operating conditions.In the frame of the proposed research project it is intended to use a smooth, unstructured reference surface as well as several microstructured surfaces made of aluminum and copper. With regard to the contact angle enlargement, the surfaces are subjected to an electrochemical treatment in addition to the application of the laser manufacturing technique. Through this step, a nanostructuring is to be achieved on the surfaces, which should lead to reduced surface energy and larger contact angles at the liquid-wall boundary, in order finally to achieve an intensification of the heat transfer.From the experiments, determining influencing factors (contact angle / hysteresis, surface roughness, operating pressure, etc.), which can significantly influence the entire condensation process, will be identified by temporally and spatially high-resolved measurements on heat transfer and surface wetting and their interdependencies with respect to topography changes will be shown. Furthermore, the contribution of nano-micro-structures on heat transfer together with the wetting characteristics should be modelled mathematically by using of measured values and should be validated with the available literature and experimental data.